Linux From Scratch - Version JH-20120423

Chapter 4. Final Preparations

4.1. About $LFS

Throughout this book, the environment variable LFS will be used. It is paramount that this variable
is always defined. It should be set to the mount point chosen for the
LFS partition. Check that the LFS variable
is set up properly with:

echo $LFS

Make sure the output shows the path to the LFS partition's mount
point, which is /mnt/lfs if the
provided example was followed. If the output is incorrect, the
variable can be set with:

export LFS=/mnt/lfs

Having this variable set is beneficial in that commands such as
mkdir $LFS/tools can be
typed literally. The shell will automatically replace
“$LFS” with
“/mnt/lfs” (or whatever the
variable was set to) when it processes the command line.

Do not forget to check that $LFS is set
whenever you leave and reenter the current working environment (as
when doing a su to
root or another user).